The present invention relates to an epitaxial wafer of gallium arsenide phosphide for use in the production of a light emitting diode.
A gallium arsenide phosphide (GaAs.sub.1-x P.sub.x) having a mixed crystal ratio "x" ranging from 0.5 to 1 has conventionally been epitaxially grown on a semiconductor substrate and doped with nitrogen for generating an iso-electronic trap. A PN junction is subsequently produced in the epitaxial layer, thereby producing the light emitting diode, hereinafter referred to as LED, which emits red, orange, yellow, green or similar lights, having an emission peak wavelength of from 550 nm to 650 nm.
The carrier concentration in the epitaxial layer of the gallium arsenide phosphide mixed crystal, in which layer the PN junction is formed, has been in the range of from 3.times.10.sup.16 to 2.times.10.sup.17 /cm.sup.3. A carrier concentration of from 9.times.10.sup.15 to 3.times.10.sup.17 /cm.sup.3 is stated in the Japanese Laid Open Patent Applications Nos. 53-64488 and 53-66388. Since the LED having the carrier concentration mentioned above exhibits a low luminance, a relatively high electric power has been necessary to increase the luminance. There has been a demand to develop a low electric power and high luminance LED to be used in an indicating device containing CMOS LSI, which has recently been broadly used. The electric power consumed in the LED should be low in accordance with the low electric power consumption in the CMOS LSI.